1. Field of the Technical Disclosure
The present disclosure relates generally to analog to digital converters (ADC), and more specifically to a residue signal generator architecture with reduced number of switches for use in a pipeline ADC that processes differential signals.
2. Related Art
Analog to Digital Converters (ADCs) are used to generate a sequence of digital codes representing the strength of an input signal at corresponding time instances. A pipeline ADC is a type of ADC which contains a sequence of (pipeline) stages, with each stage resolving a number of bits forming a sub code. The sub codes generated by various stages are used to generate a final digital code corresponding to the analog input sampled by the ADC. Assuming the final digital code is N-bits wide, each of the sub-codes may be P bits wide, with P being less than N.
Each stage (except the last stage) of a pipeline ADC generates a residue signal which is the difference of the corresponding input signal and the analog equivalent of the sub-code generated by the stage. Thus, the residual signal may be viewed as representing that portion of the input signal that needs to be resolved by subsequent stages. The residue signal represents a difference of the voltage of the input signal to the stage and the voltage level corresponding to the sub-code provided by the stage. A circuit block in a stage that generates the residue signal is generally referred to as a residue signal generator (residue block).
The architecture of a residue block generally refers to the interconnection of constituent circuit components in the block. A residue block is typically implemented using several switches used to connect different reference voltages to corresponding internal components during operation to generate the residue signal.
A pipeline ADC may process single-ended or differential signals. A differential signal generally refers to a signal whose strength (e.g., voltage) is not referenced (measured with respect to) to a fixed voltage node such as a ground terminal, but instead is measured across a pair of terminals (differential terminals) on which they are provided. In contrast, single-ended signals are provided on a single conductor and the strength is generally measured with respect to a ground terminal.
It is often desirable to reduce the number of components in an integrated circuit, for reasons such as reduced space requirement, power consumption, etc. Accordingly, it may be desirable to reduce the number of switches in a residue block of a pipeline ADC as well.
Several aspects of the present invention provide a residue signal generator architecture with reduced number of switches for use in a pipeline ADC processing differential signals.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.